Turbomachines are widely utilized in fields such as power generation. For example, a conventional gas turbine system includes a compressor section, a combustor section, and at least one turbine section. The compressor section is configured to compress air as the air flows through the compressor section. The air is then flowed from the compressor section to the combustor section, where it is mixed with fuel and combusted, generating a hot gas flow. The hot gas flow is provided to the turbine section, which utilizes the hot gas flow by extracting energy from it to power the compressor, an electrical generator, and other various loads.
A typical compressor for a gas turbine may be configured as a multi-stage axial compressor and may include both rotating and stationary components. A shaft drives a central rotor, which has a number of annular rotors, e.g., rotor wheels. Rotor stages of the compressor rotate between a similar number of stationary stator stages, with each rotor stage including a plurality of rotor blades secured to a rotor wheel and each stator stage including a plurality of stator vanes secured to an outer casing of the compressor. The rotor wheels of the several stages may be joined together, such as with axially oriented fasteners, e.g., bolts. During operation, airflow passes through the compressor stages and is sequentially compressed, with each succeeding downstream stage increasing the pressure until the air is discharged from the compressor outlet at a maximum pressure.
The hot gas flow provided to the turbine section impinges on a plurality of rotor blades, sometimes referred to as “buckets,” causing them to rotate. The rotor blades are typically annularly arranged around a rotor wheel which is mounted on a shaft, such that the hot gas flow to the turbine section impinging on the rotor blades will cause the wheel to rotate, which in turn causes the shaft to rotate. The rotation of the shaft may be used to, e.g., power the compressor or electrical generator, etc., as mentioned above. A typical turbine section includes a plurality of stages, e.g., three stages, axially spaced along the shaft. Each stage generally includes a rotor wheel with a plurality of rotor blades thereon, and the rotor wheels of the several stages may be joined together, such as with axially oriented fasteners, e.g., bolts.
Oxide dispersion strengthened alloys possess advantageous properties which may be useful in various components of a turbomachine, e.g., rotor wheels. For example, oxide dispersion strengthened alloys of nickel may have high-temperature creep strength which may be useful in hot gas path components of a turbine, e.g., turbine rotor wheels. As another example, oxide dispersion strengthened alloys of steel may be advantageous in components such as the rotor wheel of the compressor. The advantageous properties of oxide dispersion strengthened alloys derive at least in part from the grain structure of the matrix material and the dispersion of very small oxide particles within the matrix material. As a result, oxide dispersion strengthened alloys are not suitable for many welding processes. For example, fusion welding processes may alter the structure and/or distribution of the oxide particles which can have a deleterious effect on the advantageous properties of the oxide dispersion strengthened alloys.